Speaker
Description
The ultrafast Transient Liquid-Assisted Growth (TLAG) [1–5] presents an outstanding opportunity to fabricate low-cost, high-throughput superconducting REBa₂Cu₃O₇ (RE = Y or other rare earth elements, REBCO) films using scalable methods. TLAG enables the growth of epitaxial superconducting films at rates ranging from 100 to 5000 nm/s. However, the fast kinetics of this non-equilibrium process require in-situ techniques to understand its growth mechanism and determine the key process parameters.
Specialized instrumentation was developed to investigate the dynamics of the TLAG process through in-situ monitoring of precursor reactions, intermediate phase evolution, and the formation of the final REBCO superconducting phase using in-situ X-ray Diffraction (XRD) at the Energy Transition CSIC-ALBA Joint Laboratory (ETJL). The setup allows precise control of key process parameters, including temperature, partial oxygen pressure, total pressure, and heating rate, while also enabling ultrafast changes (within a fraction of a second) in both total and partial oxygen pressures. In addition, Mass Spectrometry is used to monitor gaseous reaction products, while in-situ electrical resistance measurements are performed throughout the entire growth process, providing valuable information on the conductivity changes associated with phase transformations and on the growth rate of the superconducting layer.
The electronic structure associated with Cu atoms in the REBCO lattice plays a central role in determining the superconducting properties of these materials.Therefore, in-situ X-ray Absorption Spectroscopy (XAS) experiments were also conducted to investigate the fingerprint of the transient liquid by tracking the evolution of the Cu absorption edge, revealing changes in the Cu oxidation state within the temperature (T) and partial oxygen pressure (Pₒ₂) regions of interest. A fast acquisition approach (100 ms per point), based on selecting a single photon energy corresponding to the Cu¹⁺ edge feature, enabled real-time monitoring of oxidation state changes during the ultrafast growth process. This information is very relevant for the understanding of the REBCO phase formation given the fact that the electronic structure associated with Cu atoms plays a central role in the REBCO lattice and corresponding properties.
The local coordination and electronic structure of Cu atoms were further investigated by XAS at the ESRF synchrotron (Grenoble) at the ID24-DCM beamline, which enables the acquisition of spectra with a spatial resolution of 1 µm². These measurements were combined with X-ray Fluorescence (XRF) mapping to probe the local elemental distribution within the REBCO films. The high spatial resolution and fast acquisition capabilities of ID24-DCM are especially relevant for the fast-screening methodology, in which a gradual compositional variation is introduced into a single sample by inkjet printing. This approach allows many mixed rare-earth (RE₁+RE₂) compositions to be investigated in a single experiment. Combining these synchrotron experiments with machine-learning-based data analysis represents a necessary step towards accelerating knowledge generation.
In summary, the in-situ XRD and XAS techniques implemented at ALBA synchrotron provide complementary time-resolved structural, electronic, and chemical information during the growth process under different processing conditions. When combined with the high-spatial-resolution XAS and XRF mapping performed at ESRF, they generate a unique and highly complementary dataset. Altogether, this approach enables the definition of an optimized processing window for the TLAG method, permitting the unraveling of the TLAG process to reach fundamental insight into the ultrafast growth of REBCO superconducting films.
[1] L. Soler et al. 2024, Nat Commun 11, 344, https://doi.org/10.1038/s41467-019-13791-1
[2] L. Saltarelli et al. Advanced Materials 2025, e10660, https://doi.org/10.1002/adma.202510660
[3] L. Saltarelli et al. 2022, ACS Applied Mater. Interf. 14, 43, 48582, http://dx.doi.org/10.1021/acsami.2c11414
[4] T. Puig et al. 2024, Nature Reviews Physics, 6, 132–148, https://doi.org/10.1038/s42254-023-00663-3
[5] E. Ghiara et al. 2026 Advanced Materials Technologies, 11, e70944, https://doi.org/10.1002/admt.70944